This invention relates to an objective or lens system which may be described as having extremely high speed with an extended field of view, and is particularly useful for cinematographic purposes. It is of the same general type as the lenses disclosed in U.S. Pat. No. 3,915,558, granted Oct. 28, 1975 for an invention of Erhard Glatzel, one of the joint inventors named in the present application. The present invention may be regarded as an improvement on the lenses disclosed in said patent.
The objective of the present invention complies with certain rules or conditions stated below, which differentiate the present objective from the lens system disclosed in said patent. It is found that when these rules are followed, a lens can be constructed to have a larger effective aperture than the maximum aperture disclosed in said patent, the enlargement of aperture being sufficiently great so that the lens may properly be described as being an extremely high speed objective. At the same time, a very high quality of image is produced, with adequate correction of aberrations. The angular field of view of the present lens is somewhat less than the angular field of view of the lens disclosed in said patent, but the angular field of the present lens is sufficiently large for practical purposes, especially when the lens is used for cinematographic purposes, for which it is particularly suitable.